1. Field of the Invention
The present invention relates to a hand pattern switching apparatus suitable for easily operating equipment incidental to or installed in a vehicle, such as a side mirror, an air conditioner and audio equipment, without touching the operation panel or disturbing driving of the vehicle.
2. Description of the Related Art
It has been proposed to obtain the operating information on a vehicle-mounted equipment by taking an image of a part of a driver's body (e.g., a left hand) by a camera and recognizing the image pattern, as a technique of operating the vehicle-mounted equipment without touching the operation panel (refer to Jpn. Pat. Appln. KOKAI Publication No. 11-134090). It has also been proposed to obtain the information for operating the vehicle-mounted equipment by detecting the shape and gesture of a driver's hand (refer to Jpn. Pat. Appln. KOKAI Publication No. 2001-216069).
Such a technique is realized by a pattern recognizing process to recognize the shape of a hand, for example, from the image of the hand, and a motion detecting process to detect the motion of a hand by tracing the changes in the position of the recognized hand. It is called here a hand pattern switching apparatus or the like for the sake of convenience.
When a vehicle-mounted equipment is operated by using the above-mentioned hand pattern switching apparatus, it is necessary to detect the shape and motion of a driver's (operator's) hand securely and exactly. A hand includes a palm and fingers, and the words “palm” and “fingers” will be used hereinafter depending on the situation. It is first necessary to recognize exactly what part of the image of a driver's (operator's) hand is a hand or a palm.
It is necessary to separate a hand from the background when recognizing a hand from the image of the hand. The hand part in the image is bright (white), and the background is dark (black). Thus, a hand is extracted from the background by converting the image into white when the luminance of the image is brighter than a threshold value, and black when it is darker.
The illuminance of the environment in which the image of a driver's (operator's) hand is taken changes. This causes a problem that if the above-mentioned threshold value is fixed though the environment changes, a hand cannot be exactly extracted from the background.